The present invention relates to a gear change device for shifting a transmission mounted on a vehicle.
A gear change device for shifting a transmission comprises a select actuator for actuating a shift lever in a direction of selection and a shift actuator for actuating the shift lever in a direction of shift.
As the select actuator and the shift actuator, there are generally used fluid pressure cylinders by using a fluid pressure such as air pressure or hydraulic pressure as a source of operation. The select actuator and shift actuator employing the fluid cylinders require piping for connecting the source of fluid pressure to each of the actuators, require electromagnetic change-over valves for changing over the flow passage of the operation fluid, and require space for arranging the above components, resulting in an increase in weight of the device as a whole.
In recent years, there have been proposed a select actuator and a shift actuator constituted by electric motors as a gear change device for shifting a transmission mounted on a vehicle which is provided with neither a source of compressed air nor a source of hydraulic pressure. The select actuator and the shift actuator constituted by electric motors can be constructed in a compact size as a whole and in a reduced weight since they need neither the piping for connection to the source of hydraulic pressure nor the electromagnetic change-over valve, unlike the actuators that use fluid pressure cylinders. The actuators using electric motors, however, require a speed reduction mechanism for obtaining a predetermined operation force. As the speed reduction mechanisms, there have been proposed the one using a ball-screw mechanism and the one using a gear mechanism. However, the actuators using the ball-screw mechanism and the gear mechanism are not necessarily satisfactory in regard to durability of the ball screw mechanism and of the gear mechanism and in regard to durability and the operation speed of the electric motors.
The present applicant, therefore, has proposed a gear change device equipped with a select actuator that is excellent in durability and has a high operation speed as Japanese Patent Application No. 2001-013162. In this gear change device, the select actuator is constituted by a casing, a control shaft that is rotatably arranged in the casing and is caused to turn by the shift actuator in the direction of shift, a cylindrical shift sleeve that is arranged on the control shaft so as to slide in the axial direction and is constituted integratedly with a shift lever so as to work as a shift lever support member, a magnetic moving means arranged on the outer peripheral surface of the shift sleeve, a cylindrical fixed yoke arranged surrounding the magnetic moving means, and a pair of coils arranged inside the fixed yoke.
However, the select actuator must reliably bring the shift lever to a predetermined select position. Therefore, the select actuator in the gear change device is provided with a select position-limiting means for limiting the operation position of the shift sleeve according to the thrust that generates in the shift sleeve as the shift lever support member, in proportion of the amount of electric power fed to the pair of coils. However, the select position-limiting means utilizes a spring force which increases as the shift lever moves in the direction of selection. Therefore, the select actuator produces no sufficient driving force near the select stroke end and often fails to work. To avoid this, the electric power of an increased amount must be supplied to the pair of coils, resulting in a loss of electric power.
It is, therefore, an object of the present invention to provide a gear change device equipped with a select actuator which is capable of adding a driving force near the select stroke end.
In order to accomplish the above-mentioned object according to the present invention, there is provided a gear change device comprising:
a select actuator for operating the shift lever of a transmission in the direction of selection; and
a shift actuator for operating said shift lever in the direction of shift; wherein
said select actuator has a casing, a shift lever support member that is arranged in said casing so as to slide in the axial direction and supports said shift lever, a magnetic moving means arranged on the outer periphery of said shift lever support member, a cylindrical fixed yoke arranged surrounding said magnetic moving means, a pair of coils arranged inside said fixed yoke, and a select position-limiting means for limiting the operation position of said shift lever support member according to a thrust produced by said shift lever support member in proportion to the amount of electric power fed to said pair of coils; and further, magnetic members are arranged on both sides of said pair of coils.
The magnetic members are arranged in a bobbin on which the pair of coils are wound.